Conductor core for wire ropes and method of manufacture



April 4, 1944. C ARNOLD 2,345,864

CONDUCTOR CORE FOR WIRE ROPES AND METHOD OF MANUFACTURE Filed June 6, 1942 CORD QTRAN DID CONDUCTOR IUBIII COI D SYN. RUBBER m u 8 N O T T m ATTORNEY w 0 2m WA ma m J Patented Apr. 4, 1944 CONDUCTOR CORE FOR- WIRE ROPES AND METHOD OF MANUFACTURE James 0. Arnold, Los Angeles, Calif., assignor to Lane-Wells Company, Los Angeles, Calif., a.

corporation of Delaware Application June 6, 1942, Serial No. 446,038

Claims.

My invention relates to conductor core for wire ropes and method of its manufacture, and among the objects of my invention are:

First, to provide a conductor core which is particularly designed for use in the wire rope structure disclosed in Patents Nos. 2,043,400 and ductor under conditions of extreme heat andpressure, thereby preventing the subsequent rupturing of the insulation by internal pressure due to expansion of such substances as the external pressure on the conductor core is relieved; and

Third, to provide a conductor core for Wire ropes and method of manufacture wherein the conductor is covered by spiral wrappings of cords, each of which has been previously impregnated and coated with synthetic rubber or analogous material, and wherein the coatings on said cords are molded together to form a continuous sheath reinforced by said cords.

With the above and other objects in view, as may appear hereinafter, reference is directed to the accompanying drawing, in which:

Figure 1 is a diagrammatical view illustrating the process whereby one of the cords employed in my conductor core is impregnated and coated with a synthetic rubber material;

Figure 2 is a diagram showing the manner in which the cords are wound upon the conductor to form protective sheaths;

Figure 3 is an enlarged view of my conductor core with successive layers thereof broken away, illustrating the construction;

Figure 4 is an exaggerated and substantially diagrammatical transverse sectional view through 44 of Figure 3; and

Figure 5 is a substantially diagrammatical cross sectional view of a completed cable utilizing my conductor core.

My conductor core comprises a central cord l, preferably of seine twine, around which is wound a conductor 2 comprising a plurality of multiple wire strands. Molded over the conductor 2 is a covering of rubber 3. Around the rubber covering is a first sheath 4 which is formed by a plurality of cords 5 which have been impregnated and coated with an elastic synthetic rubberlike plastic 6. Over the first sheath 4 is a second sheath 1, alsocomprising the cords 5 and plastic coating 6. The second sheath is covered with cotton braiding 8 and around the core is wound a wire rope structure 9 as shown in Figure 5.

The cords 5 are preferably of seine twine and are wound about the conductor with a comparatively short pitch. The inner sheath is wound in one direction and the outer sheath the opposite way, so that the cords of the two sheaths cross each other. In the process of winding, as will be described hereinafter, the rubberlike synthetic coating 8 on the cords is molded together to form a continuous sheath. Rubber, as is well known, has a high dielectric strength and, unfortunately, it is attacked by oil well fluids, particularly at the elevated temperatures present in a well bore. The so-called synthetic rubber or elastic synthetics such as Thiokol, Koroseal or Vistanex are virtually impervious to oil well fluids even at the elevated temperatures encountered in a well bore. Such elastic synthetics which have the desired resistance to the well fluids are, however, inherently much weaker in dielectric strength than rubber; enough so that as distinguished from rubber they may be said to have only semi-insulating properties.

This is apparently due to the difference in effect on rubber and such elastic synthetics of the various compounds such as carbon black or zinc oxide, which are conventionally added in the course of preparing the rubber or synthetic. Carbon black, for example, has highresistance as long as the particles are not forced by pressure into intimate contact. Rubber, apparently, coats these particles, further increasing their resistance, while the elastic synthetic material does not do so, but instead tends to cohere the particles, increasing the conductivity.

Another disadvantage of elastic plastics in comparison to rubber is that under conditions of continued elevated temperature and pressure, or even moderate temperature and pressure where the forces are applied continuously, elastic synthetics tend to flow or creep. The reinforcing cords 5minimize or prevent this tendency: that is, apart from the added strength afforded by the cords, they, together with the braided cotton serving 8, held the elastic synthetic in place.

The cords are prepared as shown in Figure l. The cord 5 is drawn from a suitable supply reel into a tank H containing a wetting agent l2. The wetting agent may be in the form of a thin solution which easily penetrates the. seine cord, and which comprises one of the rubberlike synthetic materials such as Thiokol, a condensation polymer such as ethylene dichloride and sodium tetrasulphide; Koroseal, a linear polymer such as ethylene dichloride, sodium hydroxide and vinyl chloride, or Vistanex, another linear polymer of iso-butanea, iso-butylene, thinned with ethylene dichloride. The cord then passes into a dryer l3 and through an intake sleeve I4 of an extruder tank l5. The extruder tank contains any of the above named rubberlike synthetic; however in a less fluid state than the liquid [2. The cord, now coated with the rubberlike synthetic, is extruded through a die It and wrapped on a bobbin or spool 2|. The pressure within the extruder is maintained extremely high, as much as 40,000 pounds, so that a very dense coating both thoroughly impregnates and covers the cord.

The several spools or bobbins are mounted in a substantially conventional winding machine: for example, six such bobbins are mounted in a unit which is rotated about the rubber covered conductor. The rubber covered conductor and cords for the inner sheath pass into the intake sleeve 23 of an extruder tank 22, discharging through an extruder die 24. This is repeated in a second stage of the winding machine in which are six more bobbins to form a second sheath. The core, including the inner and outer sheaths, then passes through a conventional cotton braiding unit (not shown) to receive the cotton braid 8 and is then wrapped by a stranded steel shroud 9, as described in more detail in the aforementioned patents.

During the process of forming the sheaths 4 and 1 the temperature of the rubberlike synthetic material is maintained at a molding and pressure point at which it tends to fuse so that the several cords are molded together by the rubberlike synthetic to form an impervious tubular sheath, without cracks or voids between the cords.

It should be borne in mind that the illustration is exaggerated and that the cords are mere threads in size, the whole core being approximately one-fourth of an inch or less in diameter for a finished cable of approximately it; of an inch. Inasmuch as heat and molding temperatures are applied during the formation of the inner and outer sheath, the rubber may be only partially cured initially, receiving its complete cure simultaneously with the application of the inner and outer sheath.

The strength of the core is materially increased by the cords 5. Twelve cords, each having a breaking strength of 27 pounds, will increase the strength of the core by 324 pounds. Of course, a. greater or lesser number of cords may be used. The rubberlike synthetic provides slight resiliency, but because of the high molding pressure it is not extremely elastic, so that undue elongation is avoided.

Various changes and alternate arrangements may be made within the scope of the appended claims, in which it is my intention to claim all novelty inherent in the invention.

I claim:

1. A conductor core for wire ropes subjected to extreme conditions'of pressure and temperature, comprising; a conductor; a molded rubber covering for said conductor having high insulation properties; inner and outer sheaths o! semi-insulating rubberlike synthetic material substantially insoluble in heated petroleum products covering said molded rubber; and helically wound reinforcing cords impregnated by the material of said sheaths and completely embedded in their respective sheaths, the cords in one sheath wound helically in the opposite direction to the cords of the other sheath whereby, in crossing, said cords form a gridwork restraining flowing or creeping of the material comprising said sheaths.

2. A conductor core wire rope structure comprising: a molded rubber covering for said conductor having high insulation properties; inner and outer sheaths of semi-insulating rubberlike synthetic material substantially insoluble in heated petroleum products covering said molded rubber; helically wound reinforcing cords, impregnated by the material of said sheaths and completely embedded in their respective sheaths, the cords in one sheath wound helically in the opposite direction to the cords of the other sheath whereby, in crossing, said cords form a gridwork restraining flowing or creeping of the material comprising said sheaths; braiding woven around said outer sheath; and a multiple stranded wire rope wound around said braiding.

3. A method of manufacturing a conductor core for wire ropes subjected to extreme conditions of heat and pressure, characterized by: extruding on a conductor core an insulation sleeve of rubber; impregnating and coating atnormal pressures a plurality of non-conducting cords with a solvent-diluted oil-impervious rubberlike synthetic material; further impregnating and coating said cords with less diluted rubberlike synthetic material under high pressure; helically wrapping said cords at least two layers and in opposite lays to form a grid pattern 'around said insulation while applying sufficient heat and pressure to unite the coatings thereon into a continuous sheath. I

4. A method of manufacturing a conductor core for wire ropes subjected to extreme conditions of heat and pressure, characterized by: extruding on a conductor core an insulation sleeve of rubber; applying to a plurality of non-conductor cords an oil-resistant semi-insulating material under conditions of temperature and pressure to completely impregnate and coat said cords; wrapping a plurality of said cords helically about said insulation under conditions of temperature and pressure to fuse said material into a continuous sheath; wrapping a-second layer of said cords helicallyabout said sheath in the opposite direction of the first cords and under conditions of temperature and pressure to fuse said material into a second continuous sheath.

5. A method of manufacturing a conductor core for wire ropes subjected to extreme conditions of heat and pressure, characterized by: extruding on a conductor core an insulation sleeve of rubber; impregnating and coating at nominal pressures a plurality of non-conductor cords with a solvent-diluted oil-impervious rubberlike' synthetic material; .further impregnating and coating said cords with less,,diluted rubberlike synthetic material under high pressures; wrapping a plurality of said cords helically about said insulation under conditions of temperature and pressure to fuse said material into a continuous sheath; and wrapping a second layer of said cords helically about said sheath in the opposite direction of the first cords and under conditions of temperature and pressure to fuse said material into a second continuous sheath.

JAMES C. ARNOLD. 

